Clinical Implications of Drug Abuse Epidemiology

Findings from several large-scale, population-based surveys of drug use have indicated relatively high prevalence of illicit drug use and shifts in trends in illicit drug use, for example highlighting the elevated rates of prescription drug misuse and associated morbidity and mortality from their misuse. These studies have furthered understanding of the high comorbidity of drug use disorders with other psychiatric disorders and with the HIV epidemic. Building on an understanding of this research in substance abuse epidemiology, it is important for clinicians to learn to integrate strategies for prevention, screening, and linkage to substance abuse treatment programs available for the communities they serve. On-going research supports the important role of such Screening, Brief Intervention, and Referral to Treatment (SBIRT) programs in a range of settings, including primary care, mental health, and emergency departments.

TRENDS IN SUBSTANCE USE

Large, population-based, annual surveys, such as the National Survey on Drug Use and Health (NSDUH) and the Monitoring the Future study, provide a foundation for understanding patterns of illicit drug use over time.^1,2 After reaching a peak in the late 1970s, rates of illicit drug use among adolescents generally declined during the 1980s, increased somewhat during the 1990s, then have stayed relatively stable over the past several years, although with some indication of a possible slight upward trend in recent years (Fig. 1).¹ Nevertheless, multiple such epidemiologic studies suggest that illicit drug use is relatively common in the population, with initial use typically starting in mid to late adolescence. The 2010 NSDUH data, based on surveys conducted in a representative sample of US households, indicate that approximately 8.9% of persons ages 12 and older in the United States—an estimated 22.6 million individuals—have used any illicit drug at least once during the past month, 6.9% have used marijuana, and 2.7% have used prescription-type psychotherapeutic drugs nonmedicaly.² For comparison, the 2010 NSDUH data indicate that 51.8% of respondents age 12 and older reported having had alcohol in the past month.² The 2011 Monitoring the Future data, based on surveys conducted at a representative sample of US secondary schools, found that 20.1% of 8th grade students reported having ever tried an illicit drug, 37.7% of 10th graders, and 49.9% of 12th graders, showing a rising trend in use over the course of adolescence.¹ For comparison, 33.1% of 8th graders reported having ever tried alcohol, 56.0% of 10th graders, and 70.0% of 12th graders.¹ Thus, the prevalence of illicit drug use is generally closer to that of alcohol use among adolescents than among the United States population as a whole. Data from MTF also indicate that marijuana continues to be the most commonly used illicit drug, with 16.4% of 8th graders, 34.5% of 10th graders, and 45.5% of 12th graders reporting having ever tried marijuana.¹

Fig. 1.

Trends in annual prevalence of illicit drug use, grades 8, 10, and 12. (Data from Johnston LD, O’Malley PM, Bachman JG, et al. Monitoring the future: National Survey Results on Drug Use, 1975–2011. Bethesda (MD): National Institute on Drug Abuse; 2011.)

Such large-scale surveys have found that typically drug use increases from adolescence to young adulthood then gradually declines.^1–3 Given the high prevalence of illicit substance use, it is imperative that clinicians routinely screen for use among their patients, especially among adolescents and young adults.^4–6 Of note, the American Academy of Pediatrics has recently released a policy statement on substance use SBIRT for pediatricians, encouraging widespread adoption as a part of routine adolescent primary care screening and including recommended comprehensive algorithms for SBIRT in the pediatric setting.⁷ Ideally, all clinicians would be able to offer patients integrated prevention, brief intervention, and referral to treatment services within well-coordinated health systems, although many communities still unfortunately face limited access to comprehensive drug abuse prevention and treatment services.^4–9

PRESCRIPTION OPIOID MISUSE

These ongoing surveys have also found a high prevalence of misuse of prescription drugs, such as hydrocodone and oxycodone, along with elevated rates for the problems associated with their misuse, including fatal and nonfatal opioid overdose.^10–14 The heightened concern for the high prevalence of prescription drug misuse is due in part to evidence of elevated levels of abuse among adolescents.^12,15,16 In 2011, among 12th graders, past year use of prescription drugs was reported to be 15.2%.¹

Clinicians must balance appropriately treating their patients while being alert for possible misuse of prescription opioids and other psychoactive medications such as stimulants and sedatives.^13,17–20 This balance can sometimes prove difficult, especially when treating chronic pain conditions. In general, clinicians treating persons with chronic analgesics or other psychoactive medications are advised to prescribe in limited, appropriate doses with regular follow-up appointments; to encourage the disposal of any unused medication; and to foster trusting relationships with patients in which personal and family history of substance abuse and risks of prescription medication misuse are openly discussed.^13,17–20 As possible, clinicians are advised to pursue analgesic treatment regimens that include nonopioid analgesics and include psychotherapeutic strategies for managing chronic pain, such as cognitive–behavioral therapy.^13,17–23

DRUG ABUSE AND DEPENDENCE

A proportion of persons who use illicit substances develop ongoing dysfunctional patterns of use that may constitute drug abuse or dependence. Some large, population-based studies, such as the NSDUH and the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), have included actual diagnostic categories of drug abuse and dependence as defined in the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV). Recent data from the NESARC indicate that approximately 2.0% of adults living in US households had a DSM-IV drug use disorder in the prior 12 months (1.4% abuse, 0.6% dependence), and 10.3% reported a drug use disorder at any point in their lifetime (7.7% abuse, 2.6% dependence).³ For comparison, data from the NESARC also indicate that approximately 8.5% of adults living in US households had an alcohol use disorder in the past 12 months (4.7% abuse, 3.8% dependence).²⁴

Drug use disorders were also highly associated with measures of physical, social, and occupational disability, including missed work days and repeated hospitalizations.^3,25–27 The widespread nature of drug use disorders further highlights the substantial public health problem they represent and the need for integrated SBIRT programs in a range of clinical settings serving general patient populations, including primary care and emergency department settings.^4–9

SPECIAL POPULATIONS

Although drug use disorders are found commonly throughout the population, several studies have suggested increased risk among some communities and demographic groups that may merit a heightened need for prevention and screening in clinical settings. For example, the NESARC and several other studies have shown drug use disorders to be much more common among men than among women.^2,3,28,29 Data from the NESARC have also suggested increased risk of drug use disorders among those who are younger; have less income; have less education; and have never married or are widowed, separated, or divorced.³ Data from the NESARC further suggest an especially high prevalence of drug use disorders among Native Ameri-cans: 18.4% of Native Americans reporting a drug use disorder at some point in their lifetime (11.6% abuse, 6.9% dependence).³

These findings are similar to those found in regional studies among Native Americans and call attention to the tremendous need of this community for improved access to substance abuse prevention and treatment services.^3,30–33 Although younger age does continue to be generally associated with drug use disorders, recent data from the NESARC and other studies suggest that rates have also increased among older adults who came of age during the height of the drug epidemic of the 1970s.^{2,3,29,34–36} These data suggest the possibility of rising rates of drug use disorders among future cohorts of older adults and highlight the need for geriatric clinicians to integrate drug abuse screening and referral into their assessments.^34–38

Multiple studies have found that gay, lesbian, and bisexual individuals are at increased risk for drug use, drug use disorders, and a range of conditions that are commonly comorbid with drug use disorders, including depression and suicidality.^39–44 This disproportionate drug use among sexual minorities seems to emerge in adolescence and continue into adulthood, and has been found across multiple classes of substances.^39–43

In addition, a high proportion of persons who enter into the criminal justice system in the United States have a history of substance abuse or dependence.^45,46 As such, criminal justice systems can serve as important settings for integrated drug abuse screening, brief intervention, and treatment.^45–47 Integrating such services in the criminal justice setting holds the promise not only to improve rates of drug use relapse among offenders, but also to reduce criminal recidivism related to illicit drug use.^45–47 It is important for clinicians to understand the unique epidemiologic risk profiles of the communities whom they serve and when appropriate to provided targeted screening and assessment for those at greatest risk.

COMORBID PSYCHIATRIC DISORDERS

Large-scale epidemiologic studies have also consistently shown a high degree of comorbidity of substance use disorders with other psychiatric disorders. Nationally representative studies such as the National Comorbidity Survey,⁴⁸ the Epidemiologic Catchment Area Surveys,⁴⁹ the National Longitudinal Alcohol Epidemiologic Survey,⁵⁰ and the NESARC^3,51 have all indicated that a wide range of psychiatric disorders, including mood, anxiety, and some personality disorders, are highly associated with drug use disorders. Findings from several of these studies have further suggested that anxiety, mood, and antisocial personality disorders are more highly associated with substance dependence than substance abuse.^3,52,53 In addition, when these analyses controlled for the presence of multiple psychiatric disorders, the associations between individual psychiatric disorders and drug use disorders were reduced but overall remained substantial (Table 1).³ This finding of the decreased magnitude of these associations suggests that common etiologies may underlie drug use disorders and other psychiatric disorders, findings consistent with twin and genetic studies.⁵⁴ Of note, numerous studies have found drug use disorders to be strongly associated with suicidal ideation and attempts, independent of other axis I and axis II disorders.^2,55–59 These findings also further highlight the importance of integrated drug abuse prevention, screening, and referral services in psychiatric treatment settings.^8,9,60–63 It is especially important for clinicians to recognize co-occurring substance use and psychiatric disorders and to treat them in an integrated and coordinated fashion.^8,9,61–64 Optimal treatment of either substance use or psychiatric disorders will not be achieved unless both are adequately treated.^8,9,60–63

Table 1.

Adjusted odds ratios (ORs) of 12-month DSM-IV drug use disorders and other psychiatric disorders controlling for demographic characteristics and comorbid psychiatric disorders in the NESARC study

Comorbid Disorder	ORs Adjusted for Demographic Characteristicsa			ORs Adjusted for Demographic Characteristics and Other Psychiatric Disordersb
	Drug Use Disorder OR (CI)c	Drug Abuse OR (CI)	Drug Dependence OR (CI)	Drug Use Disorder OR (CI)	Drug Abuse OR (CI)	Drug Dependence OR (CI)
Alcohol use disorder	9.0 (6.94–11.70)	6.4 (4.75–8.65)	15.0 (8.57–26.59)	5.6 (4.28–7.42)	4.5 (3.25–6.25)	7.0 (3.89–12.48)
Alcohol abuse	2.7 (1.98–3.71)	3.1 (2.18–4.50)	1.6 (0.88–3.01)	4.2 (3.03–5.85)	4.2 (2.87–6.13)	3.7 (1.79–7.58)
Alcohol dependence	9.7 (7.13–13.10)	5.7 (3.95–8.27)	18.7 (10.83–32.34)	6.8 (4.86–9.63)	4.8 (3.11–7.31)	9.0 (4.66–17.16)
Nicotine dependence	5.8 (4.41–7.63)	4.0 (2.86–5.69)	11.0 (6.89–17.56)	3.2 (2.38–4.38)	2.6 (1.76–3.79)	4.4 (2.63–7.42)
Any mood disorder	3.5 (2.66–4.53)	1.9 (1.34–2.70)	8.5 (5.27–13.64)	1.8 (1.33–2.41)	1.1 (0.73–1.67)	3.3 (1.92–5.56)
Major depressive disorder	2.2 (1.56–3.07)	1.4 (0.88–2.32)	3.8 (2.18–6.48)	1.4 (0.97–1.96)	1.0 (0.63–1.69)	2.2 (1.20–4.10)
Bipolar I	5.1 (3.35–7.80)	2.4 (1.38–4.21)	10.3 (5.75–18.62)	2.3 (1.49–3.67)	1.2 (0.61–2.24)	4.2 (2.14–8.35)
Bipolar II	2.4 (1.23–4.49)	2.1 (1.02–4.32)	2.6 (0.92–7.33)	1.2 (0.58–2.63)	1.2 (0.50–2.68)	1.4 (0.40–4.59)
Dysthymia	4.0 (2.17–7.20)	2.1 (0.85–5.25)	6.9 (3.28–14.67)	2.1 (1.15–3.84)	1.5 (0.62–3.76)	2.8 (1.16–6.67)
Any anxiety disorder	2.7 (2.05–3.67)	1.6 (1.15–2.25)	6.0 (3.74–9.55)	1.2 (0.88–1.73)	0.9 (0.62–1.34)	1.9 (1.07–3.24)
Any panic disorder	3.9 (2.58–5.87)	1.9 (1.02–3.62)	7.8 (4.31–14.05)	1.5 (0.91–2.39)	1.0 (0.49–2.10)	1.8 (0.85–3.81)
Panic with agoraphobia	5.6 (3.01–10.34)	3.2 (1.20–8.33)	9.2 (3.98–21.24)	1.7 (0.80–3.57)	1.4 (0.51–4.03)	1.5 (0.44–4.93)
Panic without aqoraphobia	3.1 (1.87–5.14)	1.4 (0.62–3.32)	6.4 (3.21–12.58)	1.3 (0.75–2.28)	0.8 (0.32–2.13)	1.8 (0.85–3.94)
Social phobia	2.6 (1.69–4.15)	1.7 (0.94–3.00)	4.5 (2.53–8.16)	1.2 (0.71–1.93)	1.1 (0.58–2.04)	1.2 (0.58–2.48)
Specific phobia	2.3 (1.65–3.21)	1.6 (1.06–2.47)	3.8 (2.14–6.73)	1.0 (0.68–1.41)	0.9 (0.58–1.46)	1.0 (0.53–2.00)
Generalized anxiety	4.5 (2.80–7.09)	2.0 (0.98–4.00)	9.5 (4.82–18.83)	1.7 (0.97–2.92)	1.1 (0.51–2.28)	2.5 (1.02–5.88)
Any personality disorder	4.1 (3.27–5.15)	2.6 (1.94–3.49)	9.6 (6.44–14.43)	2.2 (1.71–2.91)	1.8 (1.26–2.48)	3.3 (2.00–5.33)
Avoidant	3.4 (2.25–5.12)	2.0 (1.05–3.69)	6.0 (3.19–11.34)	1.3 (0.85–2.05)	1.1 (0.56–2.30)	1.3 (0.63–2.60)
Dependent	7.3 (3.65–14.54)	2.4 (0.89–6.67)	14.9 (6.36–34.71)	2.2 (1.02–4.80)	1.1 (0.37–3.20)	2.4 (0.75–7.77)
Obsessive-compulsive	2.3 (1.65–3.15)	1.4 (0.87–2.17)	4.6 (2.91–7.34)	0.9 (0.57–1.33)	0.7 (0.40–1.23)	1.2 (0.69–2.10)
Paranoid	3.5 (2.49–4.86)	2.0 (1.28–3.00)	6.7 (4.09–11.07)	1.1 (0.66–1.68)	0.9 (0.48–1.50)	1.1 (0.59–2.22)
Schizoid	3.4 (2.33–5.03)	2.1 (1.26–3.56)	5.8 (3.35–10.11)	1.5 (0.88–2.44)	1.2 (0.66–2.32)	1.5 (0.74–3.21)
Histrionic	4.5 (2.98–6.77)	2.5 (1.45–4.21)	8.4 (4.69–14.92)	1.3 (0.79–2.20)	1.0 (0.58–1.86)	1.4 (0.63–3.03)
Antisocial	6.4 (4.77–8.56)	4.3 (2.84–6.50)	9.7 (6.29–15.10)	2.9 (2.08–4.12)	2.5 (1.57–3.99)	2.6 (1.45–4.53)

Note: Significant odds ratios are highlighted in boldface.

^aOdds ratios adjusted for age, race-ethnicity, sex, education, income, marital status, urbanicity, and geographic region.

^bOdds ratios adjusted for age, race-ethnicity, sex, education, income, marital status, urbanicity, geographic region, and other psychiatric disorders.

^cCI = 99% confidence interval.

Data from Compton WM, Thomas YF, Stinson FS, et al. Prevalence, correlates, disability, and comorbidity of DSM-IV drug abuse and dependence in the United States: results from the National Epidemiologic Survey on Alcohol and Related Conditions. Arch Gen Psychiatry 2007;64:566–76.

COMORBID HIV INFECTION WITH DRUG USE

Research on substance abuse epidemiology has also continued to examine the high degree of comorbidity of drug use with the ongoing HIV epidemic. Injection drug use remains an important risk factor for HIV infection, with an estimated 12% of persons with newly diagnosed HIV infections in the United States in 2009 reporting this as a contributing risk factor.⁶⁵ In addition, epidemiologic research has called increasing attention to the role that noninjection drug use has also played in fueling the epidemic.⁶⁶ Drugs such as methamphetamine are well-known to increase libido, reduce inhibitions, and cloud judgment, increasing the likelihood of high-risk behaviors that individuals might not have otherwise engaged in were it not for their drug use.^67,68

A recent randomized, controlled trial among men who have sex with men who were methamphetamine dependent found that the addition of mirtazapine to substance use counseling significantly decreased not only methamphetamine use, but was also associated with decreases in a range of sexual risk behaviors.⁶⁹ Reductions in sexual risk behavior outcomes were associated with reductions in methamphetamine use among participants.⁶⁹ Larger scale replication trials are suggested, but the study findings highlight the importance of integrated prevention and treatment strategies for HIV and drug use disorders.

Multiple researchers now emphasize the importance of studying these comorbid epidemics of HIV and drug use disorders, along with other psychiatric disorders, as uniquely intertwined and fueled by a host of related social factors, referring to the combined phenomenon as a “syndemic.”^70–72 Examining the multiplicity of factors related to these combined epidemics holds promise to shed new insights into the unique burden of these epidemics on some communities, in particular men who have sex with men and ethnic/racial minorities.^70,72,73 Multiple studies have suggested the value of combined, integrated approaches to the treatment of HIV, substance abuse, and mental health, with benefits including improved adherence to HIV treatment and improved HIV outcomes.^74–77 In particular, several studies have shown that combined opioid use disorder and HIV treatment is feasible and can be associated with improved initiation of antiretroviral therapy and improved CD4 counts.^74–76

GENETIC EPIDEMIOLOGY OF DRUG USE DISORDERS

Of the various risk factors for drug use disorders, family history has been identified as one of the most consistently and strongly associated factors. Large-scale family studies have consistently suggested the clustering of drug use disorders in families, and twin and adoption studies have provided support for the important role of genetic factors in this clustering.^54,78 Multiple such studies have shown significantly increased risk of substance use disorders in first-degree relatives and children of persons with a substance use disorder.^79–81 Moreover, genetic studies have provided substantial evidence for the combined role of genetic and environmental factors in drug use disorders.

Several studies have indicated that drug use disorders, but not drug use itself, are significantly associated with genetic factors.⁵⁴ This finding suggests the important role of developmental and environmental factors in determining who is exposed to and initiates illicit drug use, with genetic factors then contributing in determining an individual’s risk of going on to develop a drug use disorder. For example, findings from several studies, including a large, longitudinal cohort study, suggest that childhood self-control—which itself is likely influenced by genetic, developmental, and other environmental factors—is strongly predictive of adult drug use disorders and a range of other outcomes, including adult physical health, income, and criminal involvement.^82–86 Such research suggests that interventions that target improved childhood self-control could have profound influence on a range of individual and societal outcomes, including rates of substance use, despite the role of other genetic and environmental factors in influencing these outcomes.^85,86 As with many common human disorders, it is likely that factors associated with drug use disorders include a large host of multiple possible genes, each exerting a small degree of influence, multiple developmental and environmental factors, and complex interactions among these factors.^{54,81,86–88} Although still in its infancy, this research promises one day to improve clinicians understanding of the unique risk and protective factors affecting individual patients, for example, possibly allowing providers to assess which patients have unique opioid receptor polymorphisms that might place them at increased risk of prescription opioid misuse.^89–91

SUMMARY

Research on the epidemiology of illicit drug use disorders provides continued critical insights into the distribution and determinants of drug use and drug use disorders in the United States. This research serves as a foundation for understanding the etiology of these disorders, helping to disentangle the complex interrelationship of developmental, genetic, and environmental risk and protective factors. Building on an understanding of this research in substance abuse epidemiology, it is important for clinicians to understand the unique trends in drug use in the overall communities that they serve and the unique risk factors for given individuals. The generally high prevalence of substance use disorders, along with their high comorbidity with other psychiatric disorders and with the HIV epidemic, make prevention, evaluation, and referral for treatment for drug abuse an important part of routine clinical practice in a range of clinical settings, including primary care, psychiatric, and emergency department settings. Ongoing efforts to ensure insurance coverage parity for the treatment of mental health and substance use disorders offer the promise of continued improvements in the integration and availability of such services in the broader US health care system.^92,93

KEY POINTS.

• Illicit drug use and drug use disorders are relatively common with initial use typically starting in mid to late adolescence and with marijuana as the most commonly used substance.

• Multiple studies have shown elevated prevalence of misuse of prescription drugs, such as hydrocodone and oxycodone, along with elevated rates for the problems associated with their misuse, including fatal and nonfatal opioid overdose.

• Large-scale epidemiologic studies have consistently shown a high degree of comorbidity of substance use disorders with other psychiatric disorders.

• Optimal treatment of either substance use or comorbid psychiatric disorders will not be achieved unless both are adequately treated.

• Genetic factors play an important role in the development of drug use disorders.

• Screening, Brief Intervention, and Referral to Treatment (SBIRT) programs for drug use should be an integral part of routine clinical care in a range of clinical settings, including primary care, psychiatric, and emergency department settings.